Entropy-mediated microstructure engineering of AlxMo0.5NbTa0.5TiZr high-entropy alloy coatings for enhanced mechanical properties

Abstract

The design of amorphous-crystalline heterostructure coatings often involves a complicated and uncertain deposition process. Achieving simple deposition progress of amorphous-crystalline heterostructure is crucial for developing high-performance protective coatings. This study proposes an innovative preparing strategy for amorphous-crystalline heterostructure by alternating mixing entropy of refractory high-entropy (RHEA) alloy coating that enhances the mechanical properties without sacrificing its excellent corrosion resistance. Amorphous-crystalline heterostructure Al_0.5Mo_0.5NbTa_0.5TiZr RHEA coating, composed of an upper crystalline layer and a bottom amorphous layer, was successfully fabricated via one-step magnetron sputtering. The influences of Al content and deposition temperature on the microstructure, mechanical properties, and corrosion resistance were investigated and the underlying mechanism was clarified. The formation of the amorphous-crystalline heterostructure can be attributed to a combined effect of the reduced mixing entropy and increased deposition temperature. Its nano-hardness (H), elastic strain failure strength (H/E), and plastic deformation strength (H³/E²) exceed those of its counterpart, i.e., AlMo_0.5NbTa_0.5TiZr RHEA coating deposited at 500 °C, reaches 11.08 ± 0.30 GPa, 0.070 ± 0.001, 0.054 ± 0.003 GPa, respectively, which are significantly better than traditional refractory metallic coatings and other amorphous RHEA coatings reported in literature. Notably, the E_corr and I_corr of the present amorphous-crystalline heterostructure coating are comparable to those of amorphous Al_0.5-RT and Al₁–500 coatings, indicating that the present amorphous-crystalline heterogeneous structure combines the advantages of both amorphous and crystalline structures, maintaining good mechanical properties while also ensuring excellent corrosion resistance.